Pressure sensitive copy paper employing dibenzylamino fluoran compounds

ABSTRACT

NEW FLUORAN COMPOUNDS CONTAINING A DIBENZYLAMINO GROUP OR A NUCLEAR SUBSTITUTED DERIVATIVE THEREOF ARE PROVIDED BY A NOVEL METHOD INVOLVING THE REACTION OF AN AMINOFLUORAN AND A BENZYL CHLORIDE IN THE PRESENCE OF ALKALI IN AN INERT NON-POLAR ORGANIC SOLVENT. THE DIBENZYLAMINO FLUORANS ARE INCORPORATED AS A REMARKABLY EFFECTIVE COLOR FORMER IN PRESENCE SENSITIVE COPYING PAPER.

United States Patent Olfice 3,824,119 Patented July 16, 1974 Ser. No. 288,993 -Claims priority, application Japan, July 8, 1970, t 45/597 Int. Cl. B41c 1/06; B41111 5/00 its. c1. 117-36.2 Claims ABSTRACT OF THE DISCLOSURE This is a division of application Ser. No. 123,069, filed Mar. 10, 1971.

BACKGROUND OF THE INVENTION Fundamentally, pressure sensitive copying paper con sists of two sheets of paper, the lower surface of the upper leaf having applied thereto minute capsules containing a color reactive achromatic substance (hereinafter called a color former) dissolved in a low volatile solvent and the upper surface of the lower leaf being coated with a solid acid, such as acid clay, phenolic compounds, etc. When the lower surface of the upper leaf and the upper surface of the lower leaf are put together and pressure is applied to the upper surface of the upper leaf by handwriting or typing, the capsules under pressure are broken and the color former contained therein is absorbed by the solid acid on the upper surface of the lower leaf to develop a color, thus providing a copy. There is also a type of pressure sensitive copying paper having a mechanism to develop color when a regional pressure is exerted upon a sheet of paper holding capsules, which contain a color former, and a solid acid on or within it. However, such type is quite similar to the first mentioned pressure. sensitive copying paper consisting of two sheets of paper, an upper and lower leaf with respect to the mechanism of color formation, and thus the same color former ,can be used for both types.

As the color former, various kinds of chemical compounds have been used, and, among others, the fiuoran compounds have recently been occupying an important position in the pressure sensitive copying paper industry because of the rich variety'of colors that such compounds develop and'the high color-developing speeds.

For example, 3,6-dimethoxy fiuoran (Beilstein Hauptwerk, Vol. XIX, p. 225) readily develops into yellow; 7-chloro-6-methyl-3rdiethylamino'fluoran (Japanese Pat. Publn. No. 21,199/ 1968) into yellowish red; rhodamine lactone (Beilstein Hauptwerk, Vol. XIX, p. 344) into bluish -red;; and 3-diethylamino-7-methylamino fiuoran (CanadianPat. No. 814,948) into green-brackish green. Among the above-mentioned derivatives and homologues, many of them have become commercially available as dyes for pressuresensitive copying paper.

SUMMARY OF THE INVENTION 'jWe have discovered new fiuoran compounds containing a dibenzylarnino group or its nuclear substituted derivatives represented by the following general formula I (this compound will, hereinafter, be referred to as dibenzylamino fluoran compound) In the above formula R and R are individually hydrogen, halogen or methyl; R is hydrogen, halogen or lower alkyl; R, and R are individually methyl or ethyl; and n is a integer from 1 to 5. R R R R and R can be concurrently in any combination. In the case where R R or R are halogen, chlorine and bromine are preferred. As a color former for pressure sensitive copying paper, the new fiuoran compounds are outstanding in the significant requirements of color developing speed, developed color density, light resistance after color development and solubility thereof. In making the novel pressure sensitive copying paper, the compounds are dissolved in a low volatile solvent and packed in minute capsules which are used in conjunction with a solid acid.

DETAILED DESCRIPTION Unfortunately, known manufacturing methods, when applied to the dialkylamino-dibenzylamino fluorans, are high in cost due to the low yield of end product and the intricacy of the process involved. For purposes of the invention, we have considered it important to eliminate this deficiency. For example, 3-diethylamino-7-dibenzylamino fiuoran, among the compounds represented by the general formula (I), may be prepared by a conventional known method as follows:

In the equation R' represents hydrogen, methyl or ethyl, R ,-R R and): are the same as defined in the general formula I. In this case the compound (A) must first be synthesized, i.e., by dibenzylation of the corresponding amino compound. V p I For. the dibenzylation the following methods are known: (1) a reaction with benzyl chloride in alcohol (Beilstein Hauptwerk, Vol. XIII, p. 450); (.2) a reaction using sodium amide and benzyl chloride without solvent (D.R.P. 301832); and (3) a reaction with benzyl chloride in aqueous alkali solution (Beilstein 2nd Supplement, Vol. XII, p. 554). However, these methods (1) to (3) are accompanied respectively by the following defects i.e. 1) a lowering of yield due to reaction by-products, (2) the intricacy of handling sodium amide and corresponding rise in cost, and (3) the intricacy of separation and purification of the reaction products. Thus, under the circumstances it is difiicult to prepare dibenzylamino fluoran at low cost by these processes.

As a result of our continued study on the manufacturing process expressed by the following equation, we finally succeeded in developing a manufacturing process which is excellent from a practical industrial point of view, with none of the above-mentioned defects.

(In the above equation, R R and R are the same as those defined in the general formula I.)

A compound of the formula II (3 diethylamino-7- amino fluoran compound) can be very easily manufactured in accordance with the following equation and the corresponding fluoran of the invention is made by benzylation of the compound H. In this case, too, if the prior art benzylation process is used satisfactory results cannot be achieved with respect to yield, purity of the product, and the relative ease of manufacturing.

OR CaHs /N OH Ri cone. H180 C H5 C=O R1 CO OH NH:

'We found the dibenzylamino fluoran compounds can be obtained in good yield by the reaction of aminofiuoran compounds with a substantially stoichiometric quantity of benzyl chloride in a non-polar aromatic solvent, and in addition, in the presence of solid alkali compounds. In this case, the use of solid alkali compounds makes the purification and separation of the reaction product exceedingly simple, so that a high purity product suitable for practical use will-be obtained without any purification step, such as recrystallization;

As a non-polar solvent, aromatic solvents such as benzene, toluene and xylene are desirable. In contrast, highly However, solvents having a very weak polarity such as o-xylene and o-dichlorobenzene, are regarded as belonging to the class of non-polar solvents useful in the present invention.

The reaction temperatures and pressures are not critical, a wide range of temperatures 'can be'used, but the reaction is preferably conducted at the reflux temperature of the aromatic solvent. The reaction can be conducted at atmospheric pressure or at superatmospheric pressures. Reduced pressures could be used, but such pressures result in unnecessary loss of solvent. f

As the solid alakil compound potassium carbonate, sodium carbonate, caustic potash and caustic soda give the most favorable results. The alkali compound is used at least in an amount corresponding to the stoichiometric amount of aminofiuoran compound or benzyl halide. The product is recovered from the reaction mixture by conventional means, for example by precipitation with a lower alcohol or by crystallization.

In the above explanation, although fluoran compounds having a diethylamino group as a substituent in 3-position has been described in the preparation of the'benzyl substituted derivatives, those compounds having a dimethyl amino group instead of the diethylamino group can be used in the same manner. And moreover, the introduc-' tion of substituent radicals into the fluoran nucleus of the aminofiuoran will not. adversely affect the process of the present invention provided that the substituent does not drastically lower the solubility of aminofiuoran in the non-polar solvent.

Our invention is further illustrated by the following examples.

EXAMPLE 1 Preparation of 3-diethylamino-7-dibenzylamino fluoran (in I, R =R =R =H) White crystals Yield: 47 g. (83% of theoretical value) Melting point: l7l173 C.

Results of analysis: C I-1 N 0 Calculated: C, 80.56%; H, 6.01%; N, 4.95% Found: C, 79.91%; H, 6.06%; N, 4.81%.

EXAMPLE 2 Preparation of 3-diethylamino-6-methyl-7-dibenzylamino fluoran (in I, R =R =H, R =CH 4 g. of 3-diethylamino-6-methyl-7-aminofiuoran (in II, R =H, R =CH 6.3 g. of benzyl chloride, 4.14 g. of anhydrous potassium carbonate and 40 ml. of xylene are subjected to reaction in a manner similar to that ,of Example 1. a

Light ochre crystals Yield: 4.35 g. (75% of theoretical value) Melting point: 153-154.5 C.

Results of analysis: C H N O Calculated: C, 80.69%; H, 6.21%; 'N, 4.83%- Found: C, 80.51%; H, 6.30%; N, 4.66%.

EXAMPLE 3 Preparation of 3-diethylamino-7-di(p-chlorobenzyl) aminofiuoran (in I, R =R =H, R =Cl) 7.7 g. of 3 diethylamino-7-aminofiuoran, 12.9 g. ofp- I chlorobenzyl chloride, 8.3 g. of anhydrous sodium carbonate, and ml. of toluene are subjected to reaction in a manner similar to that of Example 1. i

Preparation or 3 diethylamino--methyl-7-dibenzylarnino ,5 White crystals Yield: 11.0 g. (82%of theoretical value) Melting point: 1091l0 C. I Results of analysis: C H N O 'Cl 1 i I Calculated: C, 71.81%; H, 5.04%; N, 4.41% Found: C, 74.08%;H, 5.08%; N, 4.53%.

. EXAMPLE 4 13 ghof 3-diethylarnino-S-methyIJ-aiminofiuoran (in II, R1=CH3, R =H), 16.5 g. of benzyl chloride, g. of

.anhydrous'potassiumcarbonate and 100 ml. of toluene are subjected to reaction in a manner similar to that of Example 1. r

White crystals Yield:'9.1 g. (48.3% of theoretical value) Melting point: 173-174 C.

Results of analysis:C- H ,-N O

Calculated: C, 80.69%; H, 6.21%; N, 4.83% Found: C, 80.01%; H, 6.02%; N, 4.75%.

EXAMPLE 5 Preparation of 3-diethylamino-7-di(3'-methylbenzyl) aminofluoran (in I, R =R =H, R =3'-CH 7.72-g. of 3-diethylamino-7-aminofluoran, 11.24 g. of 3-methylbenzyl chloride, 8.2 g. of anhydrous potassium carbonate and 100 ml. of toluene are subjected to reaction' in a manner similar to that of Example 1.

White crystals Yield:'6.5 g. (56% of theoretical value) Melting point: l74-177 C. Results of analysis: O l-1 N 0 I Calculated: C, 80.81%; H, 6.40%; N, 4.71% Found: C, 80.33%; H, 6.39%; N, 4.57%.

EXAMPLE 6 Preparation of 3 diethylamino 7-bis(2' 4'-dimethylbenzyl)amino1luoran (in I, R1=R2=H, R3=CH3 in positions of 2 and 4') 7.72 g. of 3-diethylamino-7-aminofluoran, 12.36 g.-of 2,4-dimethylbenzyl chloride, 8.28 g. of anhydrous potas- 'sium carbonate-and 80 ml. of toluene are subjected to reaction in a manner similar to that of Example 1.

White crystals Yield: 9.5 g. (76.5% of theoretical value) Melting point: 225228 C. Results of analysis: C H N O Calculated: C, 81.03%; H, 6.75%; N, 4.56% Found: C, 80.51%; H, 6.80%; N, 4.32%.

EXAMPLE 7 White crystals Yield: 10.5 g. (84% of theoretical value) Melting point: 214-216" C.

Results of analysis: C42H42N20'3 Calculated: C, 81.03%;H, 6.75%; N, 4.50% Found: C, 80.66%; H, 6.75%; N, 4.36%.

EXAMPLE 8 Preparation of 3-diethylamino-7-bis(mixed dimethylbenzyl)aminofluoran [in I, R =R =H, R =CH (placed in two of any of the positions 2', 3, 4', 5' and 6)] 75 7.72 g. of 3-diethylamino-7-aminofiuoran, 12.36 g. of mixed-dimethylbenzyl chloride (it is prepared by chloromethylating mixed yxylene with formalin and hydrochloric acid), 8.28 g. of potassium carbonate anhydride and ml. of toluene are subjected to reaction in a manner similar to that of Example 1.

'White crystals Yield: 8.5 g. (68.5% of theoretical value) Melting point: 225-228 C.

Results in analysis: C H N O Calculated: C, 81.03%; H, 6.75%; N, 4.50% Found: C, 80.01%; H, 6.92%; N, 4.31%.

EXAMPLE 9 Preparation of 3-diethylamino-6-chloro-7-dibenzylamino fluoran (in I, R =H, R =Cl, R =H) 3.4 g. of 3-diethylamino-6-chloro-7-aminofluoran, 5.1 g. of benzyl chloride, 3.18 g. of anhydrous potassium carbonate and 40 ml. of toluene are subjected to reaction in a manner similar to that of Example 1.

Light orange colored white crystals Yield: 1 g. (22.5% of theoretical value) Melting point: -105 C.

Results of analysis: C H N O C1 Calculated: C, 75.94%; H, 5.50%; N, 4.66% Found: C, 75.88%; H, 6.06%; N, 4.13%.

EXAMPLE 10 A pressure sensitive copying paper which uses 3-diethylamino 7 bis(2',5' dimethylbenzyl)aminofluoran (which was obtained in Example 7), as its color former was prepared as follows:

60 g, of gelatin and 60 g. of gum arabic were dissolved in 50 ml. of water at 40 C. Separately 6 g. of S-diethylamino 7 bis(2',5'-dimethylbenzyl)aminofluoran was dissolved in 150 g. of diphenyl chloride. Then it was added to the aqueous solution of gelatin and gum arabic, and was completely dispersed and emulsified by means of a homo-mixer. To this dispersion was added water at 50 C. to increase the volume of the dispersion to 2000 ml. Then 90 ml. of 10% acetic acid, and water at 50 C. was added with continuous stirring until the weight of the whole was increased to 4 kg. After an hours stirring, the dispersion was cooled down to below 10 C. with ice water under stirring, and 10% caustic soda was added to adjust its pH to 9. It was then gradually brought back to room temperature. It was applied to the lower surface of the upper leaf and dried.

Separately a solid acid, such as acid clay and phenolic forlpounds, was applied to the upper surface of the lower When copying was effected with the pressure sensitive copying paper consisting of the upper and lower leaves thus prepared, it immediately developed a green image with an excellent light resistance.

EXAMPLE 11 A pressure sensitive copying paper which uses the color former obtained in Example 5 was prepared as follows:

By dissolving 4 g. of 3-diethylamino-7-di(3'-methylbenzyl)aminofluoran in g. of diphenyl chloride and treating the resulting solution in the same manner as described in Example 10, an aqueous solution containing dispersed minute capsules was obtained. It was dried, by spraying, into a dust of minute capsules, which were then mixed and dispersed in a 4% xylene solution of a pphenylphenol-formaldehyde condensation product. This dispersed solution was applied to a sheet of paper and dried to make a pressure, sensitive copying paper. When a regional pressure was exerted on the coated paper, it immedlately developed a green image having an excellent light resistance.

EXAMPLE 1 A pressure sensitiv'e'copying paper which uses the colo'r former obtained in" Example'fi' Was prepared as follows:

By dissolving 4 g. of 3 diethylarnino'-" 7-;bis(2',4'-dimethylbenzyl)aminofluoran in 120 gfof diphenyl chloride and treating the resulting solution in the samemanner as described in Example 10,, an aqueous solutioncontaining dispersed minute capsules was' fobtained l his was mixed and dispersed with 8 ,g. of minute dust, oflp-pheny lis diphenyl chloride. Substantially similar results are obtained if, in place of the diphenyl chloride, the solvent of low volatility is a lower alkyl diphenyl such as methyl-, ethyl-, and propyl diphenyl or a higher alkyl benzene, such as dodecyl-, decyl-, and octylbenzene, having a boiling point of above 150 C. If the boiling point of the solvent is at least 150 C. it has suificient low volatility according to the invention.

The solid acid functions as an electron acceptive adsorbent. In lieu of those used in the previous examples zeolite, bentonite, attapulgite and silton can be used with excellent results.

What is claimed is:

1. A pressure sensitive copying paper system which comprises the incorporation in a paper sheet of capsules containing (a) a dibenzylaminofluoran compound of the formula:

wherein R and R are individually members selected from the group consisting of hydrogen, halogen, and methyl; R is a member selected from the group consisting of hydrogen, halogen and lower alkyl; R; and R are individually members selected from sen-13 the group consisting of methyl and ethyl; and n is an integer of from 1 to 5;

(b) a solvent of low volatility whereby upon the application of pressure to said paper sheet by a writing means, said capsules in the area of said writing means are ll Q 'lQQh tsiwh r byt i li i b fil' aminofiuoran is capable of reacting with an acid to form a color localized "in .th e'region 'of said writing a 1.

2. The pressure sensitive copying paper system of claim 1 wherein said acid is incorporated into the same sheet as said capsulestin fa-solidfiorm.

-.3- Theprc r se s .ve c py n p,e v,sys tem .q claim 1, wherein said acid'isc on ta ined a; solid 'form on the upper layer of a second paper sh'e'et,"said second papergsheet being? immediately zbeneatlizztlie "paper sheet containing said capsules.

4. Pressure sensitivewcopying paper. of claim 1 wherem at least one of the substituents R R and R3 is-halogen or methyl in the case of R and R or halogen'lor :lower alkyl in the case of R 5. Pressure sensitive copyingpaperoficlaim 1 wherein at least one of the substitu'ntsR Rg, and R halogen.

6. Pressure sensitive copying paper of claim 1 vvhe'rein R is halogen-or lower alkyl. I p

7. Pressure sensitive-copying paper of claim 1 wherein said fiuoran is 3-dimethylarnino-7-dibenzylamino fiuoran.

8. Pressure sensitive copying paper of claim 1 wherein said fiuoran is 3-diethylamino 7-bis(dimethylbenzyl) aminofluoran.

9. Pressure sensitive copying paper of cla'i" fl wherein said fiuoran is 3-diethylamino-6-chloro 7-dibenzylamino fiuoran. I p I 10. Pressure sensitive copyingrpaper of claim 1 wherein the fiuoran compound is 3 diethylam ino 6-methyl@7,- dibenzylamino fiuoran.

11. Pressure sensitive copying paper of claim lwherei'n the fiuoran compound is3-diethylarnino-7-di(p-chlorobenzyl)aminofluoran. v f I 12. Pressure sensitive copying paper of claiin'lwherein the fiuoran compound is 3-diethylamino 5 -methyl-7- dibenzylamino fiuoran."

13. Pressure sensitive .copying paper of claim 1 wherein the fiuoran compound is 3'-diethylamino-7-di(3-methylbenzyl)aminofiuoran.- a

14. Pressure sensitivecopy'ing paper oi -claim 1 wherein the fiuoran compound is 3-diethyl'aminov7 bis(2,3' dimethylbenzylaminofluoran. w h v I 15. Pressure sensitivecopyingpap'er.ofclaim 1 wherein the fiuoran compound is 3-diethylamino-7-bis(2',5' d i methylbenzylaminofluoran. I h

References Cited 4 j I UNITED STATES PATENTS THOMAS J. HERBERT, 111;, Primary Examiner Us. ;'c1.* XR." I I 

